Protected area coverage targets are still far from being achieved and protected area effectiveness shows major deficiencies. Climate and land use changes and pressures from increasing human populations challenge the future of protected areas. In this research we analyse the trends and effects of these drivers of change on protected areas in Spain. This Mediterranean country, a biodiversity hotspot with many different systems of protected areas, is changing from focusing on increasing protected area coverage towards also improving conservation effectiveness. A Participatory Scenario Planning (PSP) approach was developed to create four scenarios in which the evolution of the protected area system was assessed and proposals to achieve a desirable future were agreed among participants. Results show that PSP facilitates exploration of complexity and uncertainty associated with the future of protected areas understood as social-ecological systems. We conclude that greater social and institutional support and active and adaptive management are needed for protected areas in Spain to meet the coverage and effectiveness challenges ahead.